Embryo-screening 'could boost IVF success rate'

A screening test to select the best embryos for IVF could dramatically boost success rates, researchers said today.

Some 87% of women whose embryos were checked for genetic defects went on to have a healthy baby, or were about to give birth to one.

Dr Richard Scott, a specialist in 24 chromosome aneuploidy screening, said the technique had advantages over other similar tests and had been used on far more embryos – about 6,000 to date.

It hugely cuts the risk of miscarriage and can eliminate the chance of other conditions linked to chromosomal abnormality, including Down’s syndrome, Turner syndrome and Edward’s syndrome.

The test is particularly suitable for women over 35, who have a higher chance of delivering babies with genetic defects.

It can also screen for inherited forms of diseases, including cystic fibrosis and muscular dystrophy.

Dr Scott, who presented his research at the American Society for Reproductive Medicine (ASRM) in Denver, said all couples undergoing IVF should be given access to the test, which would dramatically increase success rates.

The screening involves allowing embryos to develop, then taking a biopsy to examine their chromosomes in detail.

Only those embryos with a perfect set of 46 chromosomes are selected for transfer into the woman.

Embryos with extra or missing copies of chromosomes – which are likely to result in miscarriage or conditions linked to chromosomal abnormality – are rejected.

Dr Scott, from the Reproductive Medicine Associates of New Jersey, said: “In this particular test we can get an answer in four hours, we do not have to cryopreserve (freeze) the embryos and we can implant the embryos the next day.”

In his randomised controlled trial on 80 women, the live birth rate was 87.2% for women undergoing screening compared with 68.3% for women whose embryos were transferred without the test.

All the embryos were grown for five days to blastocyst stage, giving them a better chance of surviving and developing into a healthy baby.

When compared to IVF live birth rates in Britain of about 30%, the women in this study performed “two to three times as well”, Dr Scott said.

The women were aged 34 on average, with the oldest being 42. Up to 10 patients were from the UK.

“By the time you’re in your mid-30s about 50% of embryos are abnormal, by 40, 75% are and by 42, 85 to 90% are,” Dr Scott said.

“The problem is it’s not obvious. We can’t look at an embryo in lab and say which is going to be most successful. This screening helps us pick which to put back.”

Dr Scott said the high success rate meant only one embryo needs to be transferred at a time, cutting down the risks to mother and baby from a multiple pregnancy.

He will now carry out a three-month trial on up to 500 patients to confirm his findings.

If results are positive, Dr Scott hopes clinics will offer the screening as a standard test in IVF.

He said: “It will come to the point where it’s routine because it will be better for patient care, and will provide better outcomes.”

Last year, Dr Dagan Wells from Oxford University, published results of a similar test where 66% of his patients became pregnant.

Many of these women were on their ’last chance’ at IVF – typically aged 39 with two failed IVF cycles behind them.

Dr Tony Rutherford, chairman of the British Fertility Society, welcomed the latest research and said the screening would cost between £1,000 (€1,145) to £2,000 (€2,300) per cycle, on top of the normal costs of IVF.

He said this was the first randomised trial which clearly showed a benefit but it may take two to three years to develop.

“It’s not as important in women under 35 but in women above this age it will make a significant difference to successful implantation.

“I think it’s something that’s technically challenging but if it’s held up in future research, it’s something we would clearly like to see introduced in helping to select the best embryos to be transferred.

“This is a much more comprehensive test which is looking at all chromosomes and not just the six or seven that are more likely to cause miscarriage.”